1. Field of the Invention
The present invention relates to a method for manufacturing thin-film magnetic heads having a plurality of conversion elements for use in a magnetic tape transport and a thin-film magnetic head manufactured thereby and, more particularly, to a method for manufacturing thin-film magnetic heads in which the length of transducing gaps of tracks are formed equally with high reliability.
2. Description of the Relevant Art
A thin-film magnetic head having a plurality of transducing elements is formed by forming a plurality of conversion elements by a known thin-film processing technique, such as sputtering, depositing or photoetching on one ferrite block, and fastening another ferrite block, having a surface opposed to the elements to be extremely smoothly finished to one ferrite block, by an adhesive.
In such a thin-film magnetic head manufactured by such a process, the steps of form a plurality of tracks on one magnetic head, and not solely forming transducing gaps corresponding to the tracks but merely bonding two ferrite blocks with an adhesive to simultaneously forming the respective transducing gaps are employed. Thus, the gap lengths of the transducing gaps corresponding to the respective tracks might become irregular after bonding. It is understood that such irregularity of the transducing gaps adversely influences the electromagnetic transducing characteristics of not only the thin-film magnetic head but all the magnetic heads.
For example, a process for making a read-while-write tape head and the magnetic head made thereby are disclosed in U.S. Pat. No. 4,044,392. The magnetic head disclosed in this U.S. Patent is constructed such that a plurality of write elements and a plurality of read elements are aligned on two opposed ferrite blocks and two magnetic layers and a center section sandwiched between the two magnetic layers are disposed between the blocks. Insulating pads made of aluminum oxide are disposed in the vicinity of the right and left ends of the ferrite blocks having the plurality of write elements and at the center of the elements, an insulative gap spacer formed slightly thicker than the elements is disposed on the top of the ferrite block, and the thickness of the spacer determines the write gap dimension, i.e., the transducing gap length. Slots are cut at the sides of the center section opposed to the ferrite blocks having the write elements, filled with glass therein to define write tracks. Such a magnetic head structure is clamped integrally by two bolts through a left end piece and a right end piece. A resulting structure is filled by capillary action with a low viscosity epoxy cement applied to the gap to seal and stabilize the structure. In the method disclosed in this U.S. Patent, when the two ferrite blocks and the center section are assembled, the control of clamping with the two bolts is difficult. If the ferrite blocks and the center section are clamped by a force of certain magnitude so that the insulating gap spacer is uniformly clamped, the transducing gap lengths of the tracks can be theoretically substantially uniformly set. But, since the gaps between the insulative pads and the center section become very short by clamping, the control of raising the bonding strength by supplying sufficient quantity of adhesive into the gaps by the capillary action is difficult. If sufficient quantity of adhesive cannot be fed to the very small gaps between the insulative pads and the center section, the adhesive overflows to the outer region of the surface to be originally bonded, with the result being that the bonding strength is remarkably decreased. The ferrite blocks or the center section are lifted to the medium feeding surface by a stress generated due to the overflowed adhesive aged to be thermally swelled, shrunk or to absorb the moisture in the environment to be swelled, with the result that stepwise differences of micron order might be formed partly on the medium feeding surfaces of the ferrite blocks or the center section. It is apparent that such stepwise differences cause serious defects in case of operating the magnetic head, i.e., recording and reproducing data. For example, if the center section is lifted to the ferrite block on this the elements are formed, the spacing between the medium and the transducing gap is directly affected to remarkably reduce the electromagnetic conversion characteristic. If the center section is pressed down to the ferrite block, the elements formed on the ferrite block are exposed in the vicinity of the medium feeding surface, with the result being that the elements are worn by feeding the recording medium so that the original characteristics cannot be maintained and there is a loss in reliability.